In order to meet requirement of environmental protection, the problem of how to reduce discharge of hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxide (NO.sub.x) of cars and motorcycles is an imperative issue. The conventional carburetor is used to provide proper air/fuel mixing ratios to meet the requirement of the engine at different rotation speeds. While much research has been managed, the problem of how to achieve optimal fuel consumption yet not deteriorate the engine performance is not fully solved. The conventional carburetor generally consumes more fuel to pay for the maintenance of the horsepower. Therefore, more than required fuel is consumed and the exhaust gas results in a more serious problem of air pollution.
Other researchers try to use a cam transmission mechanism for control, but the transmission mechanism is complicated while achieved control is limited.